System for Extracting Hydrocarbons From Underground Geological Formations and Methods Thereof

ABSTRACT

An ultrasonic fracking system and methods of using the same to extract hydrocarbons from underground geological formations (e.g., oil shale, coal beds, etc.) are disclosed. The system includes piezoelectric devices that are used to produce ultrasonic mechanical vibrations and induce fractures in the geological formations. In one embodiment, a system for extracting underground hydrocarbons comprises a plurality of piezoelectric devices capable of producing mechanical waves sufficient to fracture oil shale and other geological formations, a system of delivery for innocuous proppants to create a path of least resistance for enhanced hydrocarbon flow, and a vacuum pump connected to the fractures created by the piezoelectric devices to assist in removing the hydrocarbons.

FIELD OF THE INVENTION

The present invention generally relates to the field of mining (e.g.,extracting, drilling or recovering) hydrocarbons. Embodiments of thepresent invention relate to a system for extracting hydrocarbons (e.g.,hydrocarbon-based fuels) from underground formations utilizingultrasound, and methods of using the same. More specifically,embodiments of the present invention relate to a system and method forcreating controlled fractures in underground geological formations,allowing the extraction of hydrocarbons trapped therein.

DISCUSSION OF THE BACKGROUND

Increasing demands for domestic fuel sources have led to widespreadattention to a technique of underground natural gas and oil exploitationcalled hydraulic fracturing (fracking) While the technique has merit,environmental concerns have recently arisen regarding the environmentalimpacts of fracking, including possible contamination of ground water,surface water, and soil, as well as the release of greenhouse gases intothe atmosphere. Additionally, current fracking techniques have severalinefficiencies.

Natural underground oil shale and coal deposits offer an abundant supplyof petroleum and natural gas resources. Many variables must beconsidered in the application of fracking techniques to extract thesehydrocarbons. For instance, the question of whether the extraction ofnatural gas and hydrocarbons from a particular oil shale or coal bedformation is efficient and economical depends on the flow rate of thesematerials through the formation. Darcy's Law describes the flow rate ofmaterials through porous media, which is measured in

Darcy (D). The flow rates of hydrocarbons in shale and coal bedformations is low (e.g., in the 1 nD to 1 μD range), due to the lowpermeability of shale and coal. Fracking of such underground formationsmust result in a flow rate of the hydrocarbons that is sufficient toextract economically sufficient amounts of the hydrocarbons.

To achieve such flow rates, wellbores are often drilled using verticaldrilling techniques. In order increase flow rates to economical levels,underground formations are pumped with large amounts of water andchemicals (fracking fluids) at extreme pressures to achieve fracturingof the natural underground geologic formations. Materials known asproppants are then pumped into the newly created fractures to prop openthe fractures, creating paths of least (or lower) resistance forhydrocarbons to flow.

However, fracking fluids typically include a wide range of potentiallyhazardous chemicals (e.g., acids, buffering agents, bactericides,corrosion inhibitors, friction reducers, surfactants, gelling agents,etc.). Large amounts of these fracking fluids can be used in a frackingoperation (e.g., greater than 10⁶ gallons in deep oil shale deposits). Aportion of the fracking fluids can find its way into water and soil byleaking through waste pipelines transporting the fluid from the well todisposal areas and from the disposal areas themselves. Also, a portionof the fracking fluid injected into the well can remain underground. Thechemicals in the fracking fluid can migrate into aquifers, surfacewater, and soils. Thus, the use of fracking fluids can result in thecontamination of these important resources.

Presently, hydraulic fracturing techniques have multiple problems,including:

-   -   Low efficiency in capturing the released hydrocarbons;    -   Due to economic considerations, once the flow rate of the well        is past a premium flow rate, the well may be abandoned;    -   Capping the abandoned well may not eliminate leeching of        greenhouse gases into the atmosphere;    -   If left uncapped, methane (CH₄) can leach from the well into the        air, and methane is greater than 30 times more powerful in        inducing greenhouse effects than CO₂;    -   Ground and surface water and soil can be polluted by fracking        fluid and chemicals released from wells; and    -   Horizontal drilling techniques may result in seepage of natural        gas into the environment, resulting in loss of potential revenue        and significant risk of injury and death to local fauna.

An additional drawback to fracking is the release of Naturally OccurringRadioactive Materials (NORMS). These NORMS are salts of radioactivespecies which potentially can be solubilized in the presence of water.It is conceivable that ground water bodies may then be contaminated withlabile radioactive species, lending to worsening environmental damages.

Thus, new techniques for extracting hydrocarbons that lower the costs,minimize environmental impacts, and increase the efficiency ofextracting geologic hydrocarbons are needed.

SUMMARY OF THE INVENTION

Embodiments of the present invention are generally related to systemsfor extracting hydrocarbons (e.g., natural gas) from undergroundformations utilizing ultrasonic vibrations and methods of extractinghydrocarbons using such systems. More specifically, embodiments of thepresent invention relate to a system and method for creating controlledfractures in underground geological formations, allowing the extractionof hydrocarbons trapped therein.

In accordance with the present invention, a system for fracturingunderground formations utilizing ultrasonic mechanical vibrations maycomprise a plurality of piezoelectric devices for producing mechanicalvibrations capable of fracturing underground geological formations,including oil shale, coal beds, sandstone, and other geologicalformations in which hydrocarbons may be deposited. The piezoelectricdevices may be inserted into one or more wellbores, down to the positionof a geological formation containing hydrocarbons, where thepiezoelectric devices can be used to create ultrasonic vibrations in thewellbore to shake and expand existing fractures. The piezoelectricdevices are also capable of sensing resonant vibration frequencies(typically ultrasonic) of existing fractures, which can be enlarged bypulsing the formation with the detected resonant frequency(ies).

The system may also include a reversible vacuum/pump system to create apath of least or lower resistance for hydrocarbons freed from thegeological formation by the fracturing system, effectively drawing thehydrocarbons toward the surface. The vacuum/pump system may be furtherconfigured to flush an innocuous or relatively harmless fluid or gas(e.g., N₂ or air) into a wellbore as a proppant to prevent the fracturesin the geological formation from (1) closing up and/or (2) trapping thehydrocarbons contained therein.

The fracturing system may be used in a method for extractinghydrocarbons from underground geological formations by (1) determiningthe resonant frequencies of the fractures present in the geologicalformation, (2) producing vibrations at the resonant frequencies in orderto cause spreading and growth of the fractures and free the hydrocarbondeposits contained in the geological formation, (3) pumping a proppantfrom the surface into the fractures (e.g., through a wellbore) in orderto maintain the enlarged fracture and facilitate the flow ofhydrocarbons out of the formation, and (4) collecting the hydrocarbons(e.g., through the wellbore, optionally using [i] a negative pressurecreated in the wellbore by the vacuum/pump system and/or [ii] a higherpressure that may naturally be present in an underground hydrocarbondeposit).

In one embodiment, the present invention relates to a system forfracturing underground formations, comprising (a) a plurality ofpiezoelectric devices, the plurality of piezoelectric devices beingcapable of insertion into a plurality of underground wells in theunderground formation and producing and detecting a broad range ofvibrational frequencies; (b) an apparatus for receiving and interpretingdata from the piezoelectric devices regarding detected vibrationalfrequencies; and (c) an apparatus for inducing vibrations of desiredfrequencies in the plurality of piezoelectric devices.

In another embodiment, the present invention relates to a system ofextracting hydrocarbons from underground formations, comprising (a) aplurality of piezoelectric devices, the plurality of piezoelectricdevices being capable of insertion into a plurality of underground wellsin the underground formation and producing and detecting a broad rangeof vibrational frequencies; (b) an apparatus for inducing vibrations ofdesired frequencies in the plurality of piezoelectric devices; (c) anapparatus for pumping a proppant fluid into the plurality of undergroundwells; and (d) an apparatus for extracting hydrocarbons from the wells.

In another embodiment, the present invention relates to a method ofenlarging fractures in underground geological formations, comprisingembedding a plurality of piezoelectric devices capable of producingultrasonic mechanical vibrations having (or within) a predeterminedrange of frequencies in wells exposing the underground formation; andinducing the mechanical vibrations in the wells using the piezoelectricdevices to fracture the underground formation.

In another embodiment, the present invention relates to a method ofextracting hydrocarbons from an underground geological formation,comprising (1) inserting a plurality of piezoelectric devices into aplurality of wells near a deposit of hydrocarbons in the undergroundformation, (2) inducing vibrations (e.g., within a predeterminedfrequency range) in the formation using the piezoelectric devices, (3)detecting vibrations reflected by the formation and determining theresonant frequencies of fractures in the formation, (4) inducingvibrations in the formation at the resonant frequencies using thepiezoelectric devices (e.g., to shake and enlarge the existingfractures), and (5) collecting hydrocarbons released through theenlarged fractures. The method may further include flowing a proppantinto the enlarged fractures to prevent them from closing or narrowing,and to aid in freeing physisorbed hydrocarbons from the undergroundformation.

The present invention advantageously improves the efficiency ofextracting hydrocarbons from underground deposits in geologicalformations such as oil shale, coal beds, sandstone, and other geologicalformations that contain hydrocarbons. The current apparatus and methodreduce or eliminate the need for hydraulic fluids in the process offracking underground geological formations. Thus, the present inventionreduces the costs associated with hydraulic fracturing, including thecost of the hydraulic fluid (e.g., the water and the additives, such asacids, buffering agents, bactericides, corrosion inhibitors, frictionreducers, surfactants, gelling agents, etc.), the pumping and equipmentcosts for introducing the hydraulic fluids into wells, and the cost ofstoring the used hydraulic fluid once it is removed from wells. Thepresent invention also reduces or eliminates the environmental impactsof hydraulic fracking resulting from the use of fracking fluids, sincethe present invention enables fracking underground without frackingfluids. These and other advantages of the present invention will becomereadily apparent from the detailed description of various embodimentsbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the major components of a fracking systemaccording to one embodiment of the present invention.

FIG. 2 is a diagram of a probe head containing one or more variablewindow piezoelectric transducers for delivering and sensing mechanicalvibrations in an underground geological formation.

FIG. 3 is a schematic of an amplifier system for inducing mechanicalvibrations in an array of piezoelectric devices.

FIG. 4 is a flow chart of a feedback process for determining specificranges of resonance frequencies for an underground geological formation.

FIG. 5 is a diagram showing a process of extracting hydrocarbons from anunderground geological formation.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thefollowing embodiments, it will be understood that the descriptions arenot intended to limit the invention to these embodiments. On thecontrary, the invention is intended to cover alternatives, modificationsand equivalents that may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description, numerous specific details are set forthin order to provide a thorough understanding of the present invention.However, it will be readily apparent to one skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, components, andcircuits have not been described in detail so as not to unnecessarilyobscure aspects of the present invention.

So that the manner in which various features of the present inventioncan be understood in detail, a more particular description ofembodiments of the present invention, briefly summarized above, may behad by reference to various embodiments as described below and shown inthe drawings. It is to be noted, however, that the appended drawingsshow illustrative embodiments encompassed within the scope of thepresent invention, and therefore, are not to be considered limiting, forthe present invention includes additional embodiments.

The headings used herein are for organizational purposes only and arenot meant to be used to limit the scope of the description or theclaims. As used throughout this application, the word “may” is used in apermissive sense (i.e., meaning having the potential to), rather thanthe mandatory sense (i.e., meaning must). Similarly, the words“include”, “including”, and “includes” mean including, but not limitedto. To facilitate understanding, like reference numerals have been used,where possible, to designate like elements common to the figures. Forthe sake of convenience and simplicity, the terms “connected to,”“coupled with,” “coupled to,” and “in communication with,” may be usedinterchangeably, but these terms are also generally given theirart-recognized meanings

The invention, in its various aspects, will be explained in greaterdetail below with regard to exemplary embodiments.

An Exemplary Fracking System

Embodiments of the present invention generally relate to a system forinducing or enlarging fractures (fracking) in underground geologicalformations. In one aspect, embodiments of the present invention relateto a system that includes piezoelectric devices and is capable ofdetermining resonant frequency ranges of fractures in undergroundgeological formations. For example, the system is capable of producingmechanical vibrations in the resonant frequency ranges in a well toinduce further fracturing of the material in the underground geologicalformation. In one embodiment of the system, the piezoelectric devicesinclude ultrasonic piezoelectric transducers that are capable ofdetecting and producing mechanical vibrations. In another embodiment,the system further includes titanium horns coupled to the piezoelectrictransducers to enhance the mechanical vibrations of or from thepiezoelectric transducers.

FIG. 1 provides an illustration of an exemplary fracking system 100. Thesystem includes a housing 110 that may contain a pulser/receiver systemcapable of (1) producing electrical signals to be transmitted to anarray of variable window piezoelectric transducers and (2) receiving andinterpreting electrical signals from the piezoelectric transducers. Thearray of piezoelectric transducers can be contained in housing 170,which organizes and protects the array of transducers 120 as they areintroduced into an underground geological formation through a wellbore160. The piezoelectric transducers in the array may each be coupled to ahorn assembly configured to amplify the vibrations of the coupledpiezoelectric transducer. The horn assemblies are contained in thehousing 170 along with the associated piezoelectric transducers. Thepiezoelectric transducers may be coupled to the pulser/receiver systemby coupling cables 150, configured to carry electrical signals betweenthe pulser/receiver system and the piezoelectric transducers. Thefracking system may also include components for introducing an innocuousproppant material (e.g., nitrogen gas, air, etc.) into the well bore tomaintain fractures created by the fracking system in the undergroundgeological formation, and a vacuum system for creating negative pressurein the wellbore to create a path of lower (e.g., least) resistance forthe hydrocarbons released from the formation. For example, a reversiblevacuum/pump system 140 that can both reduce pressure in the wellbore 160and draw hydrocarbons toward the surface. Also, a storage tank 130 forthe proppant (e.g., N₂ gas) may be coupled with the vacuum/pump system140, such that the proppant can be introduced into the wellbore 160 bythe reversible vacuum/pump system 140.

In one embodiment, the fracking system 100 may be configured to work inseveral wellbores simultaneously. Specifically, the fracking system mayinclude one or more piezoelectric transducer arrays that can beintroduced into one or more wellbores. Each transducer array can beintroduced into a separate wellbore, and each array may contain variablewindow piezoelectric transducers that vary in the frequency ranges inwhich they can produce and detect vibrations. Additionally, thevacuum/pump system 140 may include a manifold with several wellborecouplings, each connected to a different wellbore. Thus, the vacuum/pumpsystem 140 may be used to reduce pressure and introduce proppant inmultiple wellbores simultaneously. In an alternative embodiment, thefracking system can be configured to operate on a single wellbore (e.g.,160).

Each variable window transducer array may include one or more probeheads that contain piezoelectric transducers. FIG. 2 shows a probe head230 that may house one or more piezoelectric transducers and associatedhorn assemblies (not shown). The probe head 230 can be safely introducedinto a well exposing an underground geological formation containinghydrocarbon deposits (e.g., shales, coal beds, sandstone, etc.) withoutdamage to the piezoelectric transducers and horn assemblies therein. Oneor more probe heads 230 can be introduced into a single wellbore. Theprobe head 230 may include a tough metal housing constructed of a strongmetal, such as iron, titanium, tungsten, aluminum, and alloys thereof(e.g., stainless steel), which may contain additionalcorrosion-resistant metals (e.g., chromium, zinc, nickel, etc.) or maybe coated with corrosion-resistant metals. For instance, the probe head230 may be made of titanium or steel (e.g., surgical grade stainlesssteel).

The piezoelectric transducers may be ultrasonic and polyphonic, able toproduce a range of sonic to ultrasonic vibration frequencies upon theapplication of a voltage to the transducers from a pulser/receiversystem that may be connected to the piezoelectric transducers viacoupling cables 210 (or 150, as shown in FIG. 1). The transducers arealso able to transduce mechanical vibrations into electrical signals.Thus, the piezoelectric transducers are able to act as both sensors forsonic and ultrasonic mechanical vibrations, creating electrical currentupon deformation by a mechanical vibration (the piezoelectric effect),and as oscillators for generating sonic and ultrasonic mechanicalvibrations, changing molecular or crystalline structure upon theapplication of an electrical current (electrostriction). Thepiezoelectric transducers contain a piezoelectric material that behavesin this manner, such as piezoelectric ceramics and crystals. Thepiezoelectric transducers may include one or more piezoelectricceramics, such as lead zirconate titanate (PZT), barium titanate(BaTiO₃), lead titanate (PbTiO₃), potassium niobate (KNbO₃), lithiumniobate (LiNbO₃), lithium tantalate (LiTaO₃), zinc oxide (Zn₂O₃), andsodium tungstate (Na₂WO₃); or piezoelectric crystals, such as quartz(SiO₂), gallium orthophosphate (GaPO₄), or langasite (La₃Ga₅SiO₁₄). Inone embodiment, the piezoelectric material is PZT.

The individual piezoelectric transducers within the probe head 230 canbe tuned to different vibrational frequencies, depending on thestructure of the transducer. For instance, the thickness of thepiezoelectric material can be varied, in order to cover various and/ordifferent frequency ranges. Additionally, a damping layer (e.g., a resinor metal layer, such as steel or aluminum) may be included in thetransducer in order to widen the range of vibration frequencies that thetransducer can detect and thus increase the transducer's sensitivity.

The piezoelectric transducers may also include other known components,such as electrodes for collecting and delivering electrical current toand from the piezoelectric material, an electrical connector between thepiezoelectric transducers and the coupling cables 210, electrical wiresconnecting the electrodes to the electrical connector, a housing 220 forthe electrical connector between the piezoelectric transducer and thecoupling cables 210, a housing for each piezoelectric transducer withinthe probe head 230, etc. Ultrasonic horns (not shown) may be coupled toeach of the piezoelectric transducers in a given probe head. Theultrasonic horns vibrate with the piezoelectric transducers to increasethe amplitude of the mechanical vibrations created by the piezoelectrictransducer. The ultrasonic horns may comprise titanium or aluminum.

The piezoelectric transducers can be coupled to a pulser/receiverinstrumentation system by coupling cables. FIG. 1 shows a housing 110for this pulser/receiver instrumentation system coupled to a transducerarray 120 by coupling cables 150. The pulser/receiver system may includea phase-coupled inverse frequency-spectrum analyzer, an attenuator, oneor more amplifiers, one or more display devices, and a quarter-wavefilter assembly. The pulser/receiver instrumentation system includes apulsing system for inducing high frequency mechanical vibrations in thepiezoelectric transducers and a receiving system for electrical signalscreated by the detection of vibrations by the piezoelectric transducers(e.g., the phase-coupled inverse frequency-spectrum analyzer). Thepulser section of the system can generate short, large amplitudeelectric pulses of controlled energy, which are converted into shortsonic to ultrasonic pulses (e.g., about 1 kHz to about 15 MHz, about 2kHz to about 5 MHz, about 10 kHz to about 3 kHz, or any value or rangeof values therein) when applied to a piezoelectric transducer. Thereceiver section of the system can receive and interpret the electricalsignals (e.g., currents) produced by the piezoelectric transducers whenthey are deformed by mechanical vibrations.

The receiver section may include a frequency-spectrum analyzer capableof receiving and converting the electrical signals generated by thepiezoelectric transducers into digital frequency data that can bedisplayed on a display device. Example, frequency spectrum analyzersthat may be used include the Digital Mobile Radio Transmitter Tester,model no. MS8604A, manufactured by Anritsu, and the Agilent/HP 7000xseries of spectrum analyzers.

The pulser instrumentation system may also include one or moremulti-channel amplifiers for increasing the power of the signals createdby the pulser for creating mechanical vibrations in the piezoelectrictransducers, thereby increasing the amplitude of the mechanicalvibrations of the piezoelectric transducers. The pulser andmulti-channel amplifier are capable of producing signals for inducingvibrations at multiple frequencies in multiple piezoelectric transducerssimultaneously. The receiver instrumentation may also include one ormore multi-channel amplifiers to amplify the voltage signals produced bythe piezoelectric transducers and transmitted to the receiverinstrumentation by coupling cables 150. The amplified voltage signal canbe processed and converted to digital data by the frequency-spectrumanalyzer and displayed as an output on the display device. The receiverand multi-channel amplifier are capable of receiving and processingelectrical signals (e.g., currents or voltages) from multiplepiezoelectric transducers simultaneously.

FIG. 3 is a schematic of a typical multi-channel amplifier circuit 310,including the basic components of the amplifiers and filters. Electricalsignals from one or more piezoelectric transducers 320 are received by amixer 350, which may combine the voltage signal of the transducer(s) 320with a voltage from a pre-amp 340 to boost the signal. The low passfilter (LPF) 360 filters the frequency of the electrical signal from themixer for processing in a frequency analyzer (as discussed above), andthe audio amp 370 strengthens the signal from the transducer(s) 320 toenable analysis of the electrical signals produced from thepiezoelectric transducer(s) 320. These components are utilized in afeedback loop 330 that provides real-time feedback from thepiezoelectric transducer(s) 320 regarding the changing resonantfrequencies in the underground geological formation during theultrasonic fracking process. The feedback loop 330 allows monitoring ofthe wave response of the oil shale or other material in the geologicalformation during the ultrasonic fracking process.

The presently described embodiments of an ultrasonic fracking system arenot limiting, and the invention is intended to cover alternatives,modifications and equivalents that may be included within the spirit andscope of the invention as defined by the appended claims. It is alsounderstood that various embodiments described herein may be utilized incombination with any other embodiment described, without departing fromthe scope contained herein. In addition, embodiments of the presentinvention are further scalable to allow for additional clients andservers, as particular applications may require.

An Exemplary Method for Extracting Hydrocarbons Using UltrasonicFracking

The present invention also concerns a method of extracting hydrocarbonsfrom underground geological formations using ultrasonic vibrationscreated using piezoelectric devices (e.g., a variable window transducerarray, as discussed above). One or more of the piezoelectric devices canbe introduced into each of one or more wellbores so that eachpiezoelectric device is near a hydrocarbon deposit in the undergroundgeological formation. Subsequently, a predetermined range of mechanicalvibrations can be induced in the piezoelectric device using thepulser/receiver instrumentation to induce fractures in the geologicalformation and release hydrocarbons therefrom.

FIG. 4 is a flowchart 400 for the general steps of ultrasonic fracking,including a feedback loop system for adjusting the frequencies used tofracture the underground geological formation. Once determined, thesefrequencies are used to adjust the range of ultrasonic vibrationsproduced from a piezoelectric device array for creating or extendingfractures in the underground geological formation.

The method starts at 410, and at 420, a range of vibrational frequenciesthat are predicted to induce fracturing in the underground geologicalformation (e.g., oil shale, coal bed, sandstone, or other geologicalformation that may contain hydrocarbon deposits) are introduced bypiezoelectric devices into the geological formation. Vibrations ofcertain frequencies are absorbed by fractures in the geologicalformation (resonant frequencies), and thus are attenuated when they arereflected back to the piezoelectric devices. The pulser/receiver candetermine the resonant frequencies of the geological formation, based onthe attenuation (lower or reduced amplitude) of the resonant frequenciesthat are reflected back to the piezoelectric device. At 430, theamplitudes of the resonant frequency response are determined.Determination of the resonant frequencies at 420 and of the amplitude(s)at 430 can be repeated until the resonant frequencies of the undergroundformation are mapped.

At 440, the pulser and amplifier instruments can be tuned to theresonant frequencies and amplitudes to enable further fracturing theunderground geological formation. At 450, controlled ultrasonicvibrations are induced in the piezoelectric transducers at the resonantfrequencies of the fractures in the geological formation. Theseultrasonic vibrations result in the shaking, fracturing, and/orenlarging of fractures in the geological formation. As mentioned above,the fracking system described above is capable of monitoring changes inthe resonant frequencies of the fractures in the geological formation.

At 460, the pulser/receiver instrumentation of the fracking systemcontinually or intermittently monitors changes to the resonantfrequencies of the fractures in the geological formation, in order toadjust the frequency of the ultrasonic pulses to the changing resonantfrequencies during the fracking process (e.g., at 420, via feedback loop320 in FIG. 3). Thus, FIG. 4 shows a cyclical process, wherein frequencymonitoring at 460 and analysis of the resonant frequencies at 420 and430 are ongoing, and the frequencies delivered to the piezoelectrictransducers at 440 and 450 are adjusted in response to changes detectedin the resonant frequency or frequencies of the geological formation.

More specifically, the piezoelectric devices (e.g., a probe head)comprise an array of piezoelectric transducers that are each tuned to adifferent range of frequencies in the sonic to ultrasonic range of about1 kHz to about 15 MHz (e.g., about 2 kHz to about 5 MHz, about 10 kHz toabout 3 kHz, or any value or range of values therein), which generallycovers the frequencies at which geological formations such as oil shale,coal beds, sandstone and other geological formations that containhydrocarbons absorb vibrations. The piezoelectric transducers alsoabsorb mechanical vibrations in their tuned range, and transduce thevibrations to electrical signals, which are transmitted back to thepulser/receiver instrumentation. Fractures in the geological formationwill absorb the vibrations produced by the piezoelectric device atresonant frequencies, resulting in an attenuation of the vibrations atthat resonant frequency. Thus, the piezoelectric transducers that aretuned for the frequency range that includes the resonant frequency willproduce a weaker electrical signal when the vibrations are reflected bythe geological formation. The attenuated signal allows pulser/receiverto identify the resonant frequency range. Subsequently, thepulser/receiver system may induce mechanical vibrations at the resonantfrequencies (e.g., mechanical waves 240 and their associated nodalplanes 250, shown in FIG. 2) by sending an electrical current to thepiezoelectric transducer(s) that is tuned for the range that includesthe resonant frequencies, resulting in shaking and enlargement of thefractures. For example, FIG. 2 shows a destructive mechanical vibration260 at the resonant frequency of a fracture in the underground formationinducing damage and enlargement of the fracture.

Prior to the fracking process, a series of relatively small diameterwellbores may form a horizontal x-y array on the ground surface. Thewellbores may have variable depths, thereby creating a three-dimensionalarray of wellbores penetrating the underground geological formation. Thevarying depths of each wellbore may be used to create an optimizedthree-dimensional array of the piezoelectric transducers introduced intothe wellbores. The three dimensional array may be predetermined. Groundpenetrating radar, satellite-based imagery and geologic/seismic surveydata can be used to topographically map the target geological formationfor volume, density, composition, etc. After these data are acquired(given that the properties of each geological body or locale is unique),the correct x-y positions (±0.5 m²) over the body can be identified.Precise depths for each bore hole can then be calculated.

Given that the general equation for a wave function is known,calculating the frequency windows needed on a Riemannian surface (thevolume of the geological formation, e.g., shale body) begins bycalculating the length in the time domain, then the material-dependentimpedance of the ith piezoelectric transducer array by beginning, forexample, with calculating the Lagrangian:

L _(a) ^(b)(φ)=∫_(a) ^(b)∥{dot over (φ)}(t)∥dt=∫ _(a) ^(b)(<{dot over(φ)}(t)|{dot over (φ)}(t)>_(γ(t)))^(1/2) dt

A Fourier Transform of this to the frequency domain would then permitdetermination of the frequency window for the ith transducer. Asindicated above, this is merely the expectation value. Real-time datafrom each transducer can then optimize the pulse for the ith transducer,as it relates to the NNNth transducer (NNN=next nearest neighbor),accommodating for response time of the material surrounding each. Afterthe body volume has been calibrated, each transducer can then be fittedwith the correct titanium horn, thereby allowing each transducer toconstructively, polyphonically participate in generating the disruptivemanifold. Following titanium-horn installation, a total signal gain canbe applied until the optimal power, power spectrum, and phasecharacteristics of the pulse have been achieved.

The piezoelectric devices may then be inserted into the wellbore to thepoint that they are within or near the underground geological formation.For example, a piezoelectric device connected to a fracking system 510may be lowered through a wellbore 520 into geological formation 530 (seeFIG. 5). One or more piezoelectric devices (e.g., probe heads) can beinserted into a single wellbore. Once the piezoelectric devices aresufficiently close to the geological formation 530, the ultrasonicfracking process (as described above) can commence. In the case ofvertical well bores (see, e.g., wellbore 160 in FIG. 1), thepiezoelectric devices may be introduced into the wellbores by simplylowering them into the well. However, in the case of horizontal wells(see, e.g., wellbore 520 in FIG. 5), the piezoelectric devices can beinserted into the wellbores using a drilling string or a smallmechanical tunnel-traversing vehicle.

As shown in FIG. 5, during or immediately after ultrasonic fracking,vacuum or suction may be applied to the wellbore(s) 520 to reducepressure in the opening and upper portion of the wellbore(s) 520 to drawhydrocarbons (e.g., natural gas) 550 to the surface, where it can becollected. Additionally, an innocuous proppant (e.g., N₂ gas) may bepumped into the underground geological formation in order to aid in (1)keeping the fractures in the formation (see, e.g., fractures 540 in FIG.5) open and (2) de-sequestration of natural gas components (e.g.,methane) that may be physisorbed to the material of the formation (e.g.,oil shale, coal, sandstone, etc.). Disruption of the matrix of thegeological material, followed by infusion and extraction of gases alongthe natural z-gradient of the formation (which results in greater localpressure at greater depths) is carried out as a cyclic, periodicprocess. For example, ultrasonic fracking, can be followed by infusingN₂ gas into the well bore 520 and then applying a vacuum to the wellbore520 to draw hydrocarbons 550 (see FIG. 5) freed from the formation bythe fracking process.

The presently described embodiments of a method of extracting one ormore hydrocarbons (e.g., one or more gases at room temperature andatmospheric pressure, consisting essentially of carbon and hydrogen,such as natural gas, methane, ethane, propane, butane, etc.) fromunderground geological formations using ultrasonic vibrations are notlimiting, and the invention is intended to cover alternatives,modifications and equivalents that may be included within the spirit andscope of the invention as defined by the appended claims.

Conclusion/Summary

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof. It is also understood thatvarious embodiments described herein may be utilized in combination withany other embodiment described, without departing from the scopecontained herein. In addition, embodiments of the present invention arefurther scalable to allow for additional clients and servers, asparticular applications may require.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the Claims appended hereto and theirequivalents.

What is claimed is:
 1. A fracturing system, comprising: a) one or morepiezoelectric devices capable of insertion into a well in an undergroundgeological formation and configured to produce and/or detect a range ofvibrational frequencies; b) an apparatus configured to receive andinterpret electrical signals from the one or more piezoelectric devices;and c) an apparatus configured to induce vibrations of varyingfrequencies in the one or more piezoelectric devices.
 2. The fracturingsystem of claim 1, wherein the apparatus configured to receive and/orinterpret electrical signals from the one or more piezoelectric devicesdetermines resonant vibrational frequencies of the undergroundgeological formation.
 3. The fracturing system of claim 2, wherein theinduced vibrations have a same range of frequencies as the resonantvibrational frequencies.
 4. The fracturing system of claim 1, furthercomprising a vacuum-pump apparatus configured to reduce a pressure inthe one or more wells.
 5. The fracturing system of claim 3, wherein thevacuum-pump apparatus is also configured to pump a proppant into thewell.
 6. The fracturing system of claim 1, wherein the apparatusconfigured to receive and interpret electrical signals from the one ormore piezoelectric devices comprises an amplification system configuredto increase the power of the electrical signals from the one or morepiezoelectric devices.
 7. The fracturing system of claim 1, wherein theapparatus configured to induce vibrations of varying frequencies in theone or more piezoelectric devices comprises an amplification systemconfigured to increase the amplitude of the vibrations in the one ormore piezoelectric transducers.
 8. The fracturing system of claim 1,wherein each of the one or more piezoelectric devices comprises one ormore piezoelectric transducers.
 9. The fracturing system of claim 8,wherein each of the one or more piezoelectric transducers comprises apiezoelectric material.
 10. The fracturing system of claim 8, whereineach of the one or more piezoelectric transducers is tuned to a range ofultrasonic vibrational frequencies.
 11. The method of claim 1, whereinthe fracking system is configured to extract one or more hydrocarbons,said hydrocarbon(s) comprising natural gas, methane, ethane, propane, orbutane.
 12. The fracturing system of claim 2, wherein the apparatusconfigured to receive and interpret electrical signals from the one ormore piezoelectric devices is further configured to monitor changes inthe resonant vibrational frequencies in the underground geologicalformation.
 13. The fracturing system of claim 12, wherein the apparatusconfigured to induce vibrations of varying frequencies in the one ormore piezoelectric devices is further configured to adjust thefrequencies of the induced vibrations in response to the changes in theresonant vibrational frequencies in the underground geologicalformation.
 14. A method of vibrational fracturing, comprising: a)placing one or more piezoelectric devices capable of producingmechanical vibrations in a well exposing an underground geologicalformation; b) producing mechanical vibrations with the piezoelectricdevices to fracture the underground geological formation; and c)collecting one or more hydrocarbons released from the undergroundgeological formation.
 15. The method of claim 14, further comprisingdetecting vibrations reflected by the underground formation to determineone or more resonant frequencies in the underground geologicalformation.
 16. The method of claim 15, wherein the produced mechanicalvibrations are in the range of resonant frequencies in the undergroundgeological formation.
 17. The method of claim 16, wherein the resonantfrequencies in the underground geological formation change whilefracturing the underground geological formation, and the method furthercomprises adjusting the mechanical vibrations to match the changedresonant frequencies in the underground geological formation.
 18. Themethod of claim 14, wherein the one or more hydrocarbons comprise one ormore of natural gas, methane, ethane, propane, and butane.
 19. Themethod of claim 14, wherein the produced mechanical vibrations arecomprise ultrasonic waves.
 20. A system for extracting one or morehydrocarbons from an underground geological formation, comprising: a) aplurality of piezoelectric devices, each of the plurality ofpiezoelectric devices configured to be placed into one of a plurality ofwells in the underground geological formation, and to produce and detecta range of vibrational frequencies; b) an apparatus configured toreceive and interpret data from the piezoelectric devices; c) anapparatus configured to induce vibrations of variable frequencies in theone or more piezoelectric devices; d) an apparatus configured to pump aproppant fluid into the plurality of wells; and e) an apparatusconfigured to extract the hydrocarbon(s) from the wells.